The need to store and retrieve large volumes of digital data has resulted in the need for data storage devices having ever increasing amounts of storage capacity. Data can be stored, of course, in cassettes, floppy disks, diskettes, hard disks, optical disks, and the like. However, the greater the amount of memory available, the more difficult it becomes to accurately obtain specified data with rapid access times and with maximum system fault tolerance.
Automated data storage and retrieval systems, more commonly known as libraries, jukeboxes or auto changers (collectively referred to herein as “libraries”), are frequently used when there is a need to keep relatively large amounts of data available at a cost per gigabyte which is lower than that of solid state memory. Libraries are available for optical disks, optical tapes, magnetic disks, magnetic tapes, and the like. The information storage media are often disposed within a rigid protective housing comprising a cassette or a cartridge.
A typical library contains one or more banks, columns, or walls of storage cells, one or more data storage drives, and one or more accessors to transport designated portable data storage cartridges between those storage cells and data storage drives. Each accessor generally includes a hand-like gripper mechanism to remove and/or insert the portable data storage cartridges to and from a storage cell, and to and from a data storage drive. The library may also include an input/output station through which an operator can insert or withdraw data units into and from the interior of the library.